You decide if you are too young or too old to be something or do something.  Others in your world may have opinions or even form laws regarding what you want to be or do.  Perhaps they think they have your best interests at heart or are protecting you from something.  Down through history, women, especially, have been barred from many activities and still are not encouraged to make some decisions.  Men also have been told they are too young or too old to participate.  We all need to keep freedom alive.